This invention relates to methods of controlling industrial robots in driving same, and more particularly, it to a method of controlling an industrial robot so as to cause a hand of the industrial robot to move along a predetermined path of travel.
In, for example, U.S. Pat. No. 3,909,600, a method of controlling an industrial robot is proposed wherein interval of taught points taught is interpolated at regular intervals to give an indicated speed to a robot hand, then displacements of actuators for the robot corresponding to the points of interpolation obtained are calculated, and thereafter the displacements of the actuators obtained by the calculation are compared with actual displacements of the actuators to determine any deviations, therein so as to control the driving of the actuators to control the movement of the robot hand. Stated differently, the speeds at which the actuators are to be driven are obtained in dependence upon the indicated speed of the robot hand to thereby drive the robot hand at a predetermined speed along a predetermined path of travel.
In the above proposed control method, the speed at which each actuator is driven is determined in dependence upon the speed of movement of the robot hand. Because of this, the speed at which the actuator is driven might exceed the capability of the actuation depending on the posture of the robot and the robot hand might become inoperative as a result of an error being assumed to have been committed. When this situation occurs, the robot itself would become uncontrollable and could not be driven. This would not only reduce operation efficiency of the robot but would also raise a problem with regard to the quality control of the article handled by the robot or safety management for robot operations.